ALL configuration about queue region from up layer at first will only keep in DPDK software stored in driver, only after " FLUSH_ON ", it commit all configuration to HW. Because PMD had to set hardware configuration at a time, so it will record all up layer command at first.

RTE_PMD_I40E_RSS_QUEUE_REGION_ALL_FLUSH_OFF

"FLUSH_OFF " is just clean all configuration about queue region just now, and restore all to DPDK i40e driver default config when start up.